'Everyday chemicals' linked to cancer

"Chemicals in everyday items like cosmetics linked to cancer," The Independent reports.
Research involving genetically engineered human cells found that a class of chemical called aldehydes damaged a gene that prevents cancer from developing.

Aldehydes are organic chemical compounds naturally present in the environment and also found in many man-made products and substances such as cosmetics and car exhaust fumes. Examples of aldehydes include acetaldehyde, which is created when the body breaks down alcohol and formaldehyde, used in many products, from paint to explosives.

The research centred on the BRCA2 gene. Healthy BRCA2 genes – they come in pairs – produce a protein that helps repair DNA and regulate cell growth. Mutations to the BRCA2 genes can lead to uncontrollable cell growth which can trigger breast and ovarian cancer in women, and prostate cancer in men.

In this study the researchers found that exposure to aldehydes reduces the amount of DNA repair protein the gene can make. In people who are carrying abnormal BRCA2 genes to start with – so make less repair protein in the first place – aldehydes further reduce the amount they can make. This leads to DNA damage which could progress to cancer.

This is early stage research so we cannot say what would be a safe or toxic level of exposure to aldehydes. Unless you are willing to take drastic steps, there is not much you can do to limit your exposure to aldehydes, with the important exception of sticking to the recommended weekly limits for alcohol consumption.

The study was carried out by researchers from the University of Cambridge and two Swiss institutions: the Institute of Molecular Systems Biology and the University of Zurich. It was funded by grants from the Medical Research Council.

The study was published in the peer-reviewed scientific journal Cell, on an open access basis so it is freely available to access online.

This was laboratory research which aimed to see how chemical compounds (aldehydes) present in the environment or in products we use can affect our DNA and cancer risk.

The researchers' particular focus was on what causes mutations of the BRCA2 gene which can make people susceptible to cancers including breast and ovarian. The researchers explain how normally the BRCA2 genes produce a protein that helps to maintain and repair the DNA in our chromosomes – structures in our cells which carry genetic information. Other lab studies in mice and human cells have shown that disruption to the BRCA2 gene often leads to altered chromosome structure and sensitivity to toxic chemicals.

In this study the researchers investigated the toxic effect of formaldehyde or acetaldehyde compounds, which naturally occur in the environment, are found in various products, and accumulate in our body tissues.

The experiments were conducted on various female human cancer cells. The laboratory methods are complex. Essentially the cells were incubated with formaldehyde and acetaldehyde. Following this, the researchers studied the DNA to see what effect there was on the BRCA2 protein and chromosome structure. The researchers looked at what happened when cells had two normal copies of the BRCA2 gene and when they were heterozygous, with one normal copy and one abnormal copy with a mutation.

The researchers found that aldehydes (both formaldehyde and acetaldehyde) break down the BRCA2 protein. When a person has two normal copies of the gene they are still able to produce a functional amount of the protein that repairs and maintains chromosome structure.

However, when a person only has one normal copy of the gene they are not able to produce enough of the repair protein. When the DNA replicates it then produces what are called R-loops, three-stranded nucleic acid structures. This damages the structure and stability of the chromosomes and as such could potentially lead to cancer development.

The researchers conclude that this study raises a potential model where environmental compounds could lead to cancer development in people carrying BRCA2 mutations.

This valuable laboratory study gives a further insight into how BRCA2 mutations could lead to cancer development. Aldehydes could further reduce the amount of DNA repair protein that people with an abnormal BRCA2 gene copy are able to produce.

However, we shouldn't jump to any conclusions from this. For one thing, aldehydes are naturally present in the environment, as well as included in diverse products, from cosmetics to fossil fuel. We can't lay the blame on individual products and it's difficult to completely eradicate exposure to aldehydes.

This study alone can't inform on a safe or toxic exposure level, either for people with or for people without BRCA2 mutations.

We also can't conclude that aldehydes provide the whole answer as to why people with BRCA2 mutations are susceptible to cancer.

All of us can reduce our cancer risk by avoiding smoking, taking regular exercise, limiting consumption of red meat and alcohol and avoiding excessive exposure to sunlight.